1993 Lexus SC 400FACTORY OEM SERVICE PROCEDURE

Sensor Operating Specifications

NOTE: Unless stated otherwise in test procedure, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.
AIRFLOW METER RESISTANCE

Terminals (1) Ohms °F (°C)
VS & E2 (ES300) 200-600 N/A
VC & E2 (ES300) 200-400 N/A
THA & E2 10,000-20,000 -4 (-20)
THA & E2 4000-7000 32 (0)
THA & E2 2000-3000 68 (20)
THA & E2 900-1300 104 (40)
THA & E2 400-700 140 (60)
THA & E2 200-400 176 (80)
FC & E1 Infinity N/A
(1) For connector terminal identification, see AIRFLOW METER under ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article.
AIRFLOW METER MEASURING PLATE RESISTANCE

Terminals (1) Ohms Measuring Plate Position
FC & E1 Infinity Fully Closed
FC & E1 Zero Other Than Closed
VS & E2 200-600 Fully Closed
VS & E2 (2) 20-1000 Fully Open
(1) For connector terminal identification, see AIRFLOW METER under ENGINE SENSORS & SWITCHES in SYSTEM/COMPONENT TESTS article.
(2) Resistance will change in a wave pattern as measuring plate is opened.
COLD START INJECTOR TIME SWITCH RESISTANCE

Terminals Ohms °F (°C)
STA & STJ 25-45 Less Than 59 (15)
STA & STJ 65-85 More Than 86 (30)
STA & Ground 25-85 N/A
COOLANT TEMPERATURE SENSOR RESISTANCE (1)

Temperature - °F (°C) Ohms
-4° (-20) 10,000-20,000
32 (0) 4000-7000
68 (20) 2000-3000
104 (40) 900-1300
140 (60) 400-700
176 (80) 200-400
(1) Measure resistance between sensor terminals.
EGR GAS TEMPERATURE SENSOR RESISTANCE (1)

Sensor Temperature °F (°C) Ohms
122 (50) 69,000-89,000
212 (100) 12,000-15,000
302 (150) 2000-4000
(1) Measure resistance between sensor terminals.
INTAKE AIR TEMPERATURE SENSOR RESISTANCE (1)

Terminals Ohms °F (°C)
THA & E2
ES300 2000-3000 68 (20)
LS400 200-300 68 (20)
(1) Measure resistance with ECU connector connected.
IAC VALVE RESISTANCE

Terminals (1) Ohms
B1 & S1 Or S3 10-30
B2 & S2 Or S4 10-30
(1) For connector terminal identification, see IDLE CONTROL SYSTEM in SYSTEM/COMPONENT TESTS article.
KNOCK SENSOR RESISTANCE (1)

Terminals Ohms
Terminal To Body Infinity
(1) Terminal disconnected. Replace sensor if continuity exists.
OXYGEN SENSOR HEATER RESISTANCE (1)

Sensor Temperature Ohms
68°F (20°C)
ES300 & GS300 11.7-14.3
SC300, SC400 & LS400 5.1-6.3
(1) Measure resistance between terminals +B and HT of oxygen sensor 4-pin connector. See Fig 1.
Fig 1: Testing Oxygen Sensor Heater Resistance (Typical)
G93I78194Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.